Physical inactivity is a major risk factor for cardiovascular disease, and most Americans are not physically active enough to gain any health benefits.
Physical inactivity remains a pressing public health issue. According to the updated recommendation for adults From the American College of Sports Medicine and the American Heart Association;
"To promote and maintain health, all healthy adults aged 18 to 65 yr need moderate-intensity aerobic (endurance) physical activity for a minimum of 30 min on five days each week or vigorous-intensity aerobic physical activity for a minimum of 20 min on three days each week.
In addition, every adult should perform activities that maintain or increase muscular strength and endurance a minimum of two days each week.
Because of the dose-response relation between physical activity and health, persons who wish to further improve their personal fitness, reduce their risk for chronic diseases and disabilities or prevent unhealthy weight gain may benefit by exceeding the minimum recommended amounts of physical activity."
Facts about Fitness from WebMD.
Fitness and Exercise from the National Institutesof Health
Kids and exercise fro KidsHealth.org
Topics on physical activity from American Adademy of Pediatrics
Better Health and Fitness Through Physical Activity from the American Academy of Pediatrics